The present invention is related to a method for the operation of a wind farm having two or more wind energy plants.
For the connection of wind farms to the electric mains grid, there are a plurality of grid connection regulations, which partly contain requirements and limitations for the supplied power. So-called increase limitations may also be provided in the performance requirements, which preset to a wind farm in which degree the supplied power can be increased or decreased. Concretely speaking this means that when the wind farm starts or the supply of wind increases, the power must not increase as rapidly as would be technically possible for the wind farm, but must be limited by one or plural increase ramps. In a concrete case, this may be 3.0 MW/min to the maximum and 20 MW/10 min to the maximum, for instance, wherein the increase of 3.0 MW per minute refers to the value averaged over one minute, as well as the increase of 20 megawatt refers to the average value over 10 minutes. This means that the maximum power increase of the wind farm is permitted to be 3.0 MW in one minute, but at the same time, the power increase is not permitted to be more than 20 megawatt during a period of 10 minutes.
From US 2007/0173982 A1, the entire contents of which is incorporated herein by reference, a system and a method for the control of a power increase is known. In a first alternative, starting from a power in the time point t=0, a power for the time point t=n is calculated by multiplying an initial increase limitation with the time duration and adding it to the instantaneous power value. In an alternative embodiment, a field of n power values is calculated, wherein each of the power values is calculated via the initial gradient limitation based on a starting value. By a minimum formation over the field of the future power values, a future desired value for the power is calculated. In another known method, the same consideration, which was made for future power values, is partly retrospectively performed for the past.
From EP 1 672 779 A2, the entire contents of which is incorporated herein by reference, an apparatus and a method for controlling the gradient increase is known, in which the power increase for a wind farm is controlled based on the power increase of the individual wind energy plants in the wind farm.
The present invention is based on the objective to provide a method for the operation of a wind farm, in which a farm control presets a desired value for an electric variable of the wind farm to be generated, so that a continuous increase of the electric variable takes place, and a step-like or kinked increase of the electric variable is avoided.